As already known, a ventilated brake disk is formed by two facing and mutually spaced disks, which are joined by a plurality of bridges or pins, radially and/or tangentially, spaced from each other. In this way, some cooling-promoting gaps are available between the two disks and around such pins.
As already known, the brake disk has its own natural resonance frequencies, which depend on its size, its mass and the characteristics of its material. These frequencies affect the vibrations of the brake disk and, therefore, the noisiness of the braking system. In particular, they can generate an annoying whistle when the brake pads contact the disk during braking.
Mounting a damping element on the brake disk to dampen the vibration, and therefore the noise, is already known.
U.S. Pat. No. 3,861,501 describes an elastic element having an intermediate portion arranged in a single gap between two successive pins of the brake disk. The elastic element further has a projecting end, which is coupled to the edge of a driving element arranged around the brake disk.
The solution shown in FIG. 10c of the document U.S. Pat. No. 5,855,257 corresponds to the preamble of claim 1 and teaches the use of a wire or sheet damping element, which has a wavy profile and is axially interposed between two disks of a rotor.
This solution, however, is not completely satisfactory.
In fact, no measures in this solution allow securing permanently the damping element to the rotor. At the same time, the axial pre-load with which the damping element is arranged between the two disks is not sufficient to fasten it with respect to the rotor. In other words, the coupling provided in this solution allows the relative movement of the damping element with respect to the rotor. An undesired uncoupling of the damping element caused by the centrifugal acceleration can occur because of this relative movement.
Furthermore, said relative movement is likely to result in a counterproductive effect with regard to the occurrence of resonance frequencies, and thus with regard to the noisiness of the brake disk.